I think the property management route is also a good tool, we might do that with our next rental to learn as much as we can. 

What I did:2014: Bought condo on VA for 66.5k, Used cash I saved up to buy materials and tools. 2016: Spent 2 years of Rehab.July 2016:Appraised for 120kAug 2016:Rented outAug 2016: Bought Duplex, Started renovating the side I live in.March 2017:  Duplex is fully rented out.

For my initial analysis I use tool created by Emily Du Plessis, which helps me figure out what I need in order to move forward.

Friendly - personable, polite and professional.... not a "friend or buddy".Fair - abide by all landlord tenant laws, communicate openly and honestly, no special favors for some tenants and not others.Firm - have the backbone to hold tenants accountable, stand by your written rental agreement.Fast - swift to do maintenance and repair, swift to address tenant concerns and swift to enforce the terms of the rental agreementFlexible - take into consideration extenuating circumstances and be flexible when it is warranted, but don't let tenants manipulate you or take control.Since your grandmother chose these tenants and is compromised because of her church relationship with them, do her a favor and take on the responsibility of addressing this issue as her agent.

You need very deep pockets and political connections don't hurt in order to get a property rezoned.

I agree with the comments that Zillow is one tool of many to use.

Hello BP-ers, My in-laws currently own 4 lots about 1/4 acre each in Tool, TX on Cedar Creek Lake (not on the lake, but walking distance to the lake).

If the neighbors are outside, be polite and ask if the house is vacant.

You can leverage retirement accounts or credit cards amongst various other tools. 

A good tool to have in the back of your tool bag, but not a feasible primary strategy for me I have found.